Since nodding off while driving is dangerous, technology for detecting nodding off while driving is known. A device disclosed in Japanese Unexamined Patent Application Publication No. 2011-128966A detects sleepiness of a driver by obtaining feature points from an image that has captured the face of the driver. A device disclosed in Japanese Unexamined Patent Application Publication No. 2009-223752A warns the driver when a degree of risk, which is calculated on the basis of an eye opening time and an eye closing time of the driver, exceeds a threshold value.